Direct-print photographic silver halide emulsions



United States Patent Kodak Company, Rochester, N.Y., a corporation New Jersey No Drawing. Filed (lot. 25, 1962, Ser. N 233,146 6 Claims. (Cl. 96-168) The present invention relates to photography, and more particularly to light-developable or direct-print photographic silver halide emulsions.

Radiation-sensitive papers adapted for light recording, e.g., oscillographic recording, are known. Typical of such papers are the developing-out and print-out type. The developing-out type, as the name implies, requires that the exposed material be chemically developed, fixed and washed in order to provide a stable visible image on said material. 1 The print-out type of material develops on exposure and requ res no development step. The print-out type is generally much slower than the developing-out type and the images are unstable and have a short life.

A third type of radiation-sensitive material suitable for light-Writing and oscillographic recording comprises a hydrophilic colloid-silver halide emulsion layer which, when exposed to a high intensity source of light, forms a latent image which can then be developed by exposure to a second light source of lower intensity. Such direct-writing or direct-print emulsions are faster than print-out emulsions and require no chemical development. However, many of the recording papers of this third type have a slow rate of photodevelopment and the background areas tend to build up to obscure the image on subsequent exposure to light.

It is an object of this invention to provide a new class of light-developable, direct-print, radiation-sensitive silver halide emulsions.

It is another object of this invention to provide novel photographic silver halide emulsions suitable for" pre paring direct-print recording paper having a high rate of photodevelopment.

It is another object of this invention to provide new 1 photodevelopable photographic silver halide emulsions that are characterized as having an improved density differential between the initially exposed and unexposed areas upon photodevelopment.

, It is still another object of this invention to provide new photodevelopable silver halide emulsions 'that can be optically sensitized.

It is likewise an object of this invention to provide new photodevelopable silver halide emulsions having improved speed.

It is also an object of this invention to provide new photodevelopable photographic silver halide emulsions that have improved resistance in the initially-unexposed areas to density increase upon photodevelopinent and subsequent exposure to light.

These and other objects of the invention are accomplished by incorporating into light-developable, directprint, radiation-sensitive silver halide emulsions, copper salts, tin salts and an excess of halide ions over-that necessary initially to precipitate all'of the silver as silver halide. e

As described above, copper and tin salts are used in the emulsions of the invention. Such salt addenda are in the cupric and stannous forms. Typical copper salts are cupric acetate, cupric sulfate, cupric nitrate, cupric bromide and the like. Typhical suitable tin salts include 0 "ice stannous acetate, stannous nitrate, stannous bromide and V the like. Cupric and stannous salts that can be readily incorporated in the emulsion are desirably used in accordance with usual practice. Hence, water-soluble salts and salts soluble in water-miscible solvents such as methanol,

ethanol and the like are generally used. About .5 to 120 mole percent, and preferably about 1 to 20'mole percent, based on the silver halide in the emulsion of the. tin salt is utilized. About .1 to 25 mole percent, and preferably about .5 to 5 mole percent, based on the silver halide in the emulsion of the copper salt is utilized.

At least one water-soluble halide in an amount sufficient to provide an excess of halide ions over that necessary initially to precipitate all of the silver as silver halide in the preparation thereof is utilized. More generally, about .1 to mole percent of water-soluble halide based on the silver halide in the emulsion is utilized. With respect to specific halides it is preferred to utilize about 1 to 10 mole percent of water-soluble iodide 01'' about 10 to 76 mole percent of water-soluble bromide based on the silver halide in. the present emulsions. Water-soluble bromides are particularly useful. Illustrative water-soluble halides include ammonium, calcium, lithium, magnesium, potassium, or sodium bromide, chloride or iodide.

The light-developable photographic silver halide emulsions of the invention are prepared with silver halide grains wherein a substantial amount, and preferably a predominant amount, of the sensitivity to radiation is internal to the grain. Suitable silver halides include silver chloride, silver bromide, silver bromoiodide, silver chloroiodide, and silver chlorobromoiodide. The preferred emulsions are those that are predominantly silver bromide. For a description of suitable emulsions that form latent images internal to thesilver halide grains, reference is made to Davey et al., US. Patent 2,592,250, issued April 8, 1952; Glafkides, Photographic Chemistry, vol. 1,. pp. 31-2, Fountain Press, London; and McBride application, U.S. Serial No. 222,964, filed September 11, 1962. The present silver halide emulsions generally have an average grain size of about .1 to 10 microns, and more generally .5 to 1 micron.

The internal image emulsions particularly useful in the invention are those that have higher internal sensitivity in the silver halide grains than surface sensitivity. Typically, such internal image emulsions are those which, when measured according to normal photographic techniques by coating atest portion of the emulsion on a transparent support, exposing to a light intensityscale DEVELOPER A p Grams N-methyl-p-aminophenol sulfate 0.31 Sodium sulfite, desiccated 39.6 Hydroquinone 6.0 Sodium carbonate, desiccated 18.7 Potassium bromide 0.86 Citric acid V Potassium metabisulfite 1.5

Water to make 1 liter.

4 p 3 DEVELOPER B Grams N-methyl-paminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrate i 52.5 Potassium bromide 5.0 Sodium 'thiosulfate 10.0 Water to make 1 liter.

' A wide variety of hydrophilic, water-permeable organic colloids can be suitably utilized in preparing the silver halide emulsions or dispersions of the invention. Gelatin is preferably utilized although other colloidal material such as colloidal albumin, cellulose derivatives, synthetic resins or the like can be utilized. Suitable colloids that can be used are polyvinyl alcoholor a hydrolyzed polyvinyl acetate as described in Lowe, US. Patent 2,286,215, issued June 16, 1942; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 19-26% as described in U.S. Patent 2,327,808 of Lowe and Clark, issued August 24, 1943; a water-soluble ethanolamine cellulose acetate as described in Yutzy, US. Patent 2,322,085, issued June 15, 1943; a polyacrylamide having a combined acryl-amide content of 30-60% and a specific viscosity of 025-15 on an imidized polyacrylamide of like acrylamide content and viscosity as described in Lowe, Minsk and Kenyon, US. Patent 2,541,474, issued February 13, 1951; zein as described in Lowe, US. Patent 2,563,791, issued August 7, 1951; a vinyl \alcohol polymer containing urethane carboxylic acid groups of the type described in Unruh and Smith, US. Patent 2,768,154, issued October 23, 1956; or containing cyanoacetyl groups. such as the vinyl alcohol-vinyl cyanoacetate copolymer as described in Unruh, Smith and Priest, US. Patent 2,808,331, issued October 1, 1957; or a polymeric material which results from polymerizing a protein or a saturated acylated protein with a monomer having a vinyl group as described in lllingsworth, Dann and Gates, US. Patent 2,852,382, issued September 19, 1958.

The subject photodevelopable photographic silver halide emulsions of the invention can contain the addenda generally utilized in such products including gelating hardeners, gelatin plasticizers, coating aids, optical sensitizers and the like.

The above-described emulsions of the invention can be coated on a wide variety of supports in accordance with usual practice. Typical supports for photographic elements of the invention include paper,-cellulose nitrate film, cellulose acetate film, polyvinyl acetal film, polystyrene film, polyethylene-terephthalate film and related rich in blue'and ultraviolet light such as are used in oscil-' lographs described in Heiland, US. Patent 2,580,427, issued January 1, 1952, to form a latent image in the emulsion of the photographic element, and thereafter the resulting latent'image'is photodeveloped ,byexposing it to a light source of less intensity than the original exposure such as to a conventional fluorescent light, a tungsten light, or even ordinary daylight. Generally the latent image formed in the emulsion in the first instance is not visible and does not become visible until photodevelopment. If desired, photographic elements containing the emulsions of the invention can be developed and fixed in aqueous chemical developing-out and fixing solutions after the initial exposure forming the latent image, or after the abovedescribed photodevelopment.

I have found that silver halide emulsions containing combinations of cupric salts, stannous salts and watersoluble halide salts as described herein are synergistic combinations in that results are obtained by their combination which are substantially greater than the summation of their individual eflFects. The emulsions of the invention are particularly characterized as being of improved speed and as being capable of being optically sensitized.

The invention is illustrated by the following examples of preferred embodiments thereof.

Example 1 A light-developable, direct-print, light-sensitive gelatinosilver chlorobromide emulsion bromide, 5% chloride) having high internal sensitivity and low surface sen sitivity of the type described in Davey et al., US. Patent No. 2,592,250 was prepared. To a portion of the melted emulsion was added 50 mole percent of potassium bromide and the emulsion was held for 5 minutes. Then 20 mole percent of stannous chloride dissolved inmethanol was added followed by 1.5 mole percent of cupric sulfate dissolved in water. The resulting mixture was heated to 60 C. over a 10-minute period, cooled, and coated on a photographic paper support at coverages of 110 mg. of silver per square foot and 255 mg. of gelatin per square foot. The mole percent concentrations referred to are based on the silver halide in the emulsion. The resulting coating was then exposed to a microsecond flash on an Edgerton, Germeshausen and Grier Mark VI sensitometer through a 21-step 0.15 log E neutral density step tablet followed by a photodevelopment of 5 minutes with a 60 foot-candle cool-white fluorescent light. On photodevelopment, 16 visible 0.15 log E stepsresulted. The image was intense blue on a grayish-blue background.

Example 2 A light-developable, direct-print, light-sensitive gelatinosilver chlorobromide emulsion of the type described in Example 1 was prepared and the addenda in Table 1 below were incorporated therein as described in Example 1.

TABLE 1 Eml rllsion Feature Emulsion Addenda Control.

1.5 mole percent cupric sulfate.

20 mole percent stannous chloride.

50 mole percent potassium bromide.

20 mole percent stannous chloride+1.5 mole percent cupric sulfate.

50 mole percent potassium bromide-l-L5 mole percent cupric sulfate.

50 mole percent potassium bromide-F20 mole percent stannous chloride.

50 mole percent potassium bromide-{-20 mole percent stannous ehloride+1.5 mole percent cuprie sulfate.

TABLE 2 Visible 0.15 log E Steps On Exposure and Photodevelopment Emulsion No.

(Control) -Q No negative image.

No negative image.

4 No negative image. 5

s No negative image. 7 16.

Emulsion No. 8 is an emulsion of the invention and it showed a speed increase of 2 visible 0.15 log E step or 200% over Emulsion No. 7, the latter emulsion not containing the cupric salt of the invention. The reflection densities in the image areas (D and in the background areas (D for each of the emulsions after the exposure and photodevelopment were measured, the results being summarized in Table 3 below. The densities were read under safelights using a Wratten No. 15 filter in the densitometer.

As demonstrated by the data set out in the above tables, the present combinations of stannous salts, cupric salts and water-soluble halide salts are combinations of cooperating addenda commonly referred to as synergistic combinations.

Example '3 A light-developable, direct-print, light-sensitive gelatino-silver chlorobromide emulsion of the type described in Example 1 was prepared and the addenda in Table 4 below were incorporated therein as described in Exampie 1. A combination of emulsion addenda of the invention of cupric sulfate, stannous chloride and potassium bromide was compared with a combmatlon of emulsion addenda wherein an equivalent amount of plumbous nitrate was substituted for the cupric sulfate. The effect on the emulsion of a cyanine dye of the type conventionally used to panchromatically sensitize silver halide emulsions was also determined.

TABLE 4 Feature Emulsion Addenda Control.

50 mole percent potassium bromide+20 mole percent staunous chloride+1.5 mole percent plumbous nitrate.

50 mole percent potassium bromide-H mole percent stannous chloride-+1.5 mole percent euprie sulfate.

50 mole percent potassium bromide+20 mole percent stannous chloride-H .5 mole percent plumbous nitrate +cyanine dye.

50 'mole percent potassium brom1de+20 mole percent stannous chloride+l.5 mole percent cupric sulfate +eyanine dye.

The concentrations of addenda set out in Table 4 are based on the silver halide in the emulsion. Emulsion Nos. 11 and 13 are emulsions of the invention. Emulsion Nos. 9-13 were then coated, exposed and photodeveloped as described in Example 1. Table below summarizes the number of visible 0.15 log E steps obtained for each coated emulsion, the emulsion Nos. referred to in Table 5 are those of Table 4. The cyanine dye can be the type disclosed in Brooker, US. Patent No. 1,934,- 657, dated November 7, 1933, Sprague, US. Patent No. 2,503,776, dated April 11, 1950 or the like dyes.

TAB LE 5 Visible 0.15 log E Emulsion N0. Steps After Exposure and Photo development 0 No negative image. 1 13. 11 17. 1 13. 13 18.

A speed increase of 4 visible 0.15 log E steps as shown in Table 5 for the emulsion combination of the invention (Emulsion No. 11) over a closely-related emulsion combination containing a plumbous salt in lieu of my cupric salt (Emulsion No. 10) is a speed increase of 400%. Emulsion Nos. 10-13 of Table 4 were also exposed through a Wratten No. 16 filter (filters out blue light) as Well as through the 0.15 log E step tablet. Table 6 below summarizes the number of visible 0.15 log E steps obtained for each coated emulsion.

TABLE 6 Visible 0.15105, E Emulsion No. Steps Produced by minus Blue Light on Exposure and Photodevelopment The data set out in this example illustrate that silver halide emulsions containing the addenda of the invention are substantially faster than closely-related emulsions containing plumbous salts in lieu of my cupric salts, and can be efiectively optically sensitized with cyanine dyes.

The invention has been described in considerable detail with particular reference to preferred embodiments there of, but it will be understood that variations and modifications can be eliected Within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A light-developable, direct-print, radiation-sensitive V emulsion comprising silver halide grains having a substantial amount of said radiation sensitivity internal to said grains, a hydrophilic colloid, about .5 to 120 mole percent based on said silver halide of a stannous salt, about .1 to 25 mole percent based on said silver halide of a cupric salt, and about .1 to mole percent based on said silver halide of, a water-soluble halide.

2. A light-developable, direct-print, radiation-sensitive emulsion as defined by claim 1 wherein the water-soluble halide is a water-soluble bromide.

3. A light-developable, direct-print, radiation-sensitive emulsion as defined by claim 1 wherein the hydrophilic colloid is gelatin.

4. A light-developable, direct-print, radiation-sensitive emulsion as defined by claim 1 wherein the water-soluble halide is selected from the group consisting of ammonium, calcium, lithium, magnesium, potassium and sodium bromide, chloride and iodide.

' 5. A light-developable, direct-print, radiation-sensitive gelatino-silver halide emulsion comprising silver halide grains having an average size of about .1 to 10 microns, a predominant amount of said radiation sensitivity being internal to said grains, about .5 to mole percent based on said silver halide of a stannous salt, about .1 to 25 mole percent based on said silver halide of a cupric salt, and about .1 to 100 mole percent based on said silver halide of a water-soluble bromide.

6. A light-developable, direct-print, radiation-sensitive.

gelatino-silver halide emulsion comprising silver halide 3,178,292 7 8 v grains having an average size of about .5 to 1 micron, a References Cited by the Examiner predominant amount of said radiation sensitivity being UNITED STATES PATENTS internal to sand grains and a predominant amount of said 2,504,593

silver halide being silver bromide, about 1 to 20 mole 2 910 359 32;; et 2 o I h v n percent based on said silver alide of stannous chloride 5 3,033,678 5/62 Hunt 96 94 about .5 to 5 mole percent based on said silver halide of oupric sulfate, and about 10 to 70 mole percent based on said silverhalide of potassium bromide. V NORMAN TORCHIN Primmy Examiner 

1. A LIGHT-DEVELOPABLE, DIRECT-PRINT, RADIATION-SENSITIVE EMULSION COMPRISING SILVER HALIDE GRAINS HAIVNG A SUBSTANTIAL AMOUNT OF SAID RADIATION SENSITITY INTERNAL TO SAID GRAINS, A HYDROPHILIC COLLOID, ABOUT .5 TO 120 MOLE PERCENT BASED ON SAID SILVER HALIDE OF A STANNOUS SALT, ABOUT .1 TO 25 MOLE PERCENT BASED ON SAID SILVER HALIDE OF A CUPRIC SALT, AND ABOUT .1 TO 100 MOLE PERCENT BASED ON SAID SILVER HALIDE OF A WATER-SOLUBLE HALIDE. 